It is the purpose of this project to study the biochemistry and chemical structure of histocompatibility antigens and tumor antigens. Site-directed mutagenesis, using oligonucleotide primers, is being used to relate the structure of H-2 antigens and their biological activity. F9 cells, and differentiated clones derived from them, are also studied for an understanding of the molecular mechanism involved in the expression of H-2 antigens. Synthetic cytochrome C peptides are employed to study the interaction between these antigens, the T cell receptor and the Ia restriction element. Biochemical, nucleic acid cloning and peptide synthesis are being used to study a family of different proteins which are involved in transformation. The features of the interaction of this family of proteins and the immune system are also being explored.